diff --git a/mode/perl.py b/mode/perl.py
index 461de49..f43264c 100644
--- a/mode/perl.py
+++ b/mode/perl.py
@@ -303,18 +303,12 @@ class PerlWhichFunction(Method):
     '''Show the user what function they are in'''
     def _execute(self, w, **vargs):
         cursor = w.logical_cursor()
-        i = cursor.y
-        name = None
-        while i >= 0 and name is None:
-            line = w.buffer.lines[i]
-            m = regex.perl_function.match(line)
-            if m:
-                name = m.group(1)
-            else:
-                i -= 1
+        name = w.mode.get_line_function(cursor.y)
         if name is None:
             w.application.set_error("None");
         else:
+            functions = w.mode.get_functions()
+            i = functions[name] + 1
             w.application.set_error("line %d: %s" % (i, name))
 
 class PerlHashCleanup(Method):
@@ -710,6 +704,7 @@ class Perl(mode.Fundamental):
         self.add_bindings('close-bracket', (']'))
         self.add_bindings('close-brace', ('}'))
         self.functions = None
+        self.funclines = None
 
     def build_function_map(self):
         self.functions = {}
@@ -717,6 +712,7 @@ class Perl(mode.Fundamental):
         highlights     = self.window.get_highlighter()
         curr, stack    = None, []
         for group in highlights.tokens:
+            self.funclines.append(curr)
             for t in group:
                 if not curr and t.name == 'sub':
                     curr  = t.string
@@ -729,7 +725,8 @@ class Perl(mode.Fundamental):
                         stack.pop()
                         if not stack:
                             curr = None
-            self.funclines.append(curr)
+            if curr:
+                self.funclines[-1] = curr
 
     def get_functions(self):
         if self.functions is None:
@@ -741,5 +738,9 @@ class Perl(mode.Fundamental):
         pairs.sort()
         names = [x[1] for x in pairs]
         return names
+    def get_line_function(self, y):
+        if self.funclines is None:
+            self.build_function_map()
+        return self.funclines[y]
 
 install = Perl.install